Coulomb electron pairing in a tight-binding model of La-based cuprate superconductors

TL;DR

This paper investigates how Coulomb interactions in a long-range hopping tight-binding model of La-based cuprate superconductors lead to the formation of electron pairs, potentially relevant for high-temperature superconductivity.

Contribution

It demonstrates analytically and numerically that Coulomb repulsion can produce propagating electron pairs via an effective narrow energy band in a realistic long-range hopping model.

Findings

Coulomb electron pairs form in the model and propagate through the system.

Pair formation probability peaks around 20-80% filling factor.

Long-range hopping enhances pair formation compared to nearest neighbor models.

Abstract

We study the properties of two electrons with Coulomb interactions in a tight-binding model of La-based cuprate superconductors. This tight-binding model is characterized by long-range hopping obtained previously by advanced quantum chemistry computations. We show analytically and numerically that the Coulomb repulsion leads to a formation of compact pairs propagating through the whole system. The mechanism of pair formation is related to the emergence of an effective narrow energy band for Coulomb electron pairs with conserved total pair energy and momentum. The dependence of the pair formation probability on an effective filling factor is obtained with a maximum around a filling factor of 20 (or 80) percent. The comparison with the case of the nearest neighbor tight-binding model shows that the long-range hopping provides an increase of the phase space volume with high pair formation probability. We conjecture that the Coulomb electron pairs discussed here may play a role in high temperature superconductivity.